As it stands nearly 90 per cent of people favour their right hand to their left, while in apes it’s closer to a 50/50 split. But when in human evolution did we begin to favour one hand over the other? A new study led by the University of Kansas sheds some light on the question, discovering markings on the teeth of a Homo habilis upper-jaw fossil, which suggest evidence of right-handedness as far back as 1.8 million years ago.

Handy work

Published online in the Journal of Human Evolution, the study analysed labial striations (cut marks) on the teeth of a Homo habilis fossil found in the Olduvai Gorge in Tanzania.

The striations discovered on the lip side of the frontal teeth were put under the scrutiny of a microscope to determine alignment and quantify angulation. The majority of the striations veered from left down to the right, suggesting that Homo habilis was right-handed.

The study suggests that the markings come from the usage of a stone tool, and that the early human in question used the tool with its right hand to cut food it was holding in its mouth, while pulling with the left hand.

Although brain lateralisation had been identified previously in Homo habilis and other ancestral fossils, this is the first and only example so far of pre-Neanderthal dominant handedness.

“We think that tells us something further about lateralisation of the brain,” says David Frayer of the University of Kansas and lead author of the study. “We already know that Homo habilis had brain lateralisation and was more like us than apes. This extends to handedness, which is key.”

Now that this discovery has opened the door for the origins of handedness, it is hoped that it will lead to more searches for this kind of evidence in other early Homo fossils. Though arguably not as important as language, handedness itself is an interesting aspect of how culture has developed across the globe, from the direction we write in to which way a spiral staircase spirals.

“We think we have the evidence for brain lateralisation, handedness and possibly language, so maybe it all fits together in one picture,” says Frayer. “One specimen does not make an incontrovertible case, but as more research is done and more discoveries are made, we predict that right-handedness, cortical reorganisation and language capacity will be shown to be important components in the origin of our genus.”

While this gives us some further insight into human evolutionary history, we can only hope that the left-handed members of Homo habilis had a Leftorium to visit.